The invention provides a method, system, and apparatus for aligning the index angle of a polar coordinate system device and more specifically, to a method, system, and device for aligning the index angle of a pivoting platform within a rotating device, such as the rotor of a centrifuge, with a vertical axis of a robotic end-effector.
Centrifuges are well-known devices that are used to rotate samples contained in test tubes or cassettes holding a plurality of test tubes at relatively high speeds. Centrifuges that are structured and arranged for cassettes typically include a centrifuge rotor having a plurality of arms with trunions from which can be suspended a pivoting platform, e.g., a bucket, for holding one or more cassettes. As the rotor rotates, the pivoting platforms suspended from the trunions pivot about an axis so that the test tubes in the cassettes also pivot to horizontal or near horizontal orientations.
Because centrifuges are designed to operate at high rates of speed, e.g., 4500 revolutions per minute (RPM), to ensure that the centrifuge rotor is in balance, it is important that the cassettes are inserted into the buckets and the buckets are positioned on the trunions precisely.
As robotic arms are increasingly being used for loading and unloading centrifuges, positioning cassettes and buckets requires that the end-effectors of the robotic arms, i.e., robotic grippers and the like, have a reference system that complies with that of the pivoting platform of the centrifuge rotor. This is complicated by the fact that, conventionally, end-effectors lack adequate compliance in all degrees of freedom, except for the vertical axis. Accordingly, it would be desirable to have a method, system, and apparatus for aligning the index angle of a polar coordinate system device, e.g., the pivoting platform of the centrifuge rotor, with the vertical axis of the robotic gripper.